The present disclosure relates to an electrophotographic toner, and in particular relates to a capsule toner.
A capsule toner includes cores and shell layers (capsule layers) disposed over the surface of the cores. A commonly known method of manufacturing a toner involves coating the surface of cores with shell layers while the cores, in a solid state, are dispersed in an aqueous medium having a dispersant dissolved therein.
Due to an anionic dispersant being used in such a manufacturing method, it is thought that aggregation of the cores can be inhibited if the anionic dispersant can be caused to adhere to the surface of the cores. Unfortunately, it is difficult to cause a dispersant having a small molecular weight to adhere to the surface of the cores because the dispersant has a high tendency to dissolve in the aqueous medium. On the other hand, a dispersant having a large molecular weight may function as a coagulant for large molecules and as a result tends to cause aggregation of the cores.
In consideration of the above, a technique has been proposed in which a capsule toner can be obtained without using an electrolytic material such as an anionic dispersant, by using cores that are anionic. More specifically, the aforementioned technique involves attraction of a cationic film forming material (shell layer material) toward the surface of the cores and polymeric fixing of the capsulation material (shell layer material) through in-situ polymerization to yield a dense capsule toner. In a situation in which a capsulation material (shell layer material) is attracted directly to the surface of a toner and caused to polymerize without using an anionic additive (for example, a dispersant), aggregation of toner particles does not occur during capsule formation, even if the glass transition point Tg of a binder resin—constituting a major component of the cores—is lower than the curing temperature of the shell layer material, and thus a dense capsule toner can be obtained.